Tool/software:
Hi
I am using UCC28C43 for converter Vin 200V to 640V for power rating of 15W, with transformer inductance of 720uH, switching frequency is 180kHz
Issue: When I am operating 200V gate pulses are equal, when I increase voltage to 300V pulses are alternate short and wide pulses.
I hope this issue due to high dv/dt making CS pin re
aching threshold and turning off, to compensate this next pulse will be wide enough to maintain the output voltage.
Hi,
When you see narrower and wider pulses alternating, first thing is to check if it is due to the slope compensation not properly setup. Another possibility is COMP pin voltage at a level to cause pulse on and off, or the feedback loop not stable. You need to show the waveforms about this pulses pattern to help further analysis.
This IC has no on-chip leading edge blanking. You need to adjust CS pin filter to adjust the blanking time externally.
On this below, you need to show the MOSFET Vgs waveform together - I suspect Vgs has a glitch to cause Vds glitch.
Hi
I tried increasing the slope compensation, but the issue still persists. Even under these conditions, the duty cycle remains below 50%. Therefore, I am unsure whether slope compensation is the root cause of the problem.
At 200V, the system operates at a 40% duty cycle. When I increase the voltage to 300V, the duty cycle decreases, and that’s when the issue starts to appear
Also I am attaching my schematic here for more clarity
Here is the Vgs waveform
